Chemical Forums
Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: jchoi on June 03, 2018, 02:08:23 AM
-
Hi, I have a question about electrochemistry. Will Fe dissolve in 1.0M Ce4+? If so, will Fe3+ or Fe2+ be formed?
I think I have to use E°=0.0592/n(logK) to solve this question, but I'm not sure what the value of n would be. I have the answer (Yes, and Fe2+), but would like to understand how I can arrive at that answer.
This is my first post, so feel free to let me know if there's a rule I should abide by!
-
Start by listing all related E0 potentials.
-
E° of Fe2+ = -0.41V
E° of Fe3+ = -0.04V
Since the question is asking for Fe(s) dissolving in a Ce4+ solution, I think I can reverse (take the negative of) these values to have 0.41V and 0.04V.
-
You have omitted two other important potentials.
Hint: oxidation goes in two steps, and there is also reduction involved.
No, you don't change the sign of the potential when the reaction goes in the opposite direction.
-
I think I need potentials for Ce4+ and Ce3+ but I can't find those potentials chart I have, or in other charts online. Or are the potentials from Fe3+ :rarrow: Fe2+ + e-?
Two steps as in Fe(s) :rarrow: Fe3+ :rarrow: Fe2+?
-
I think I need potentials for Ce4+ and Ce3+ but I can't find those potentials chart I have, or in other charts online.
Not for both of them, you need potentials for Ce4+ :rarrow: Ce3+ reduction. That's what will be happening in the solution.
Or are the potentials from Fe3+ :rarrow: Fe2+ + e-?
This is as wrong as it can be (check if the charges are balanced ;) ) but you are in general on the right track.
Two steps as in Fe(s) :rarrow: Fe3+ :rarrow: Fe2+?
Wrong order, but yes, it is about stepwise oxidation of Fe, not an oxidation followed by a reduction.